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Abstract

Brook trout, Salvelinusflontinalis, is an extensively harvested fish because of its
popularity as a game fish among anglers in the US. One of the primary management
tools for sustaining adequate population sizes under intense fishing pressure is to
stock hatchery-produced fish. The genetic consequences, however, of mixing the
hatchery-produced fish with wild fish is still unknown. In our study, stocking impact
was assessed in brook trout samples from multiple stocked ponds in the Adirondack
Region, Upstate New York. The wild populations (the stock pond-caught brook trout
samples that did not have tag on their intact adipose fins), some having a history of
trout stocking and others suspected of being genetically "pure", were compared with
the Temescamie strain (the stock pond-caught brook trout samples with tags on their
adipose fins), a hatchery-produced hybrid strain. The genetic variation within and
among the wild brook trout populations was characterized using microsatellite DNA
markers. We hypothesized that that completely introgressed fish populations would
show no difference from the allele frequencies in the Temescamie strain. In contrast,
individual fish or fish populations with no introgression history would have alleles,
allele frequencies and allelic diversity uncharacteristic of the Temescamie strain.
Microsatellite data revealed genetic difference between Temescamie population and
unmarked populations that rejects the complete introgression model for stocked
Adirondack ponds. Within the unmarked group, five relatively non-admixed
populations were found, and they showed lower genetic diversity than the hybrid
Temescamie strain, in addition to allele frequency differences. Insight on the genetic
variation of wild brook trout gained through this study will prove useful in shaping
management strategies to ensure the long-term viability of wild brook trout
populations in New York and elsewhere in their native range.